Method for the reduction of uranium compounds



May 12; 1959 w. H. cooKE ET AL METHOD FOR THE REDUCTION OF URANIUM COMPOUNDS Filed Oct. 7, 1943 IIIIIIIIIIIIII/ lNvENroRS I 1% g Attorney fiice 2,886,429 Patented May 2,19

METHOD FOR THE REDUCTION OF URANIUM COMPOUNDS William H. Cooke, Liverpool, and John William Croom Crawford, Frodsham, England, assignors, by mesne assignments, to the United States of America as represented by the United States Atomic Energy Commission Application October 7, 1943, Serial No. 505,322 13 Claims. (Cl. 75-844 This invention relates to improved methods for the manufacture of easily oxidisable metals, and more particularly to the manufacture of uranium.

In the manufacture of easily oxidisable metals it has been previously proposed to carry out the process in a reducing atmosphere or in an atmosphere inert to the metal. In the manufacture of uranium, for example, by reducing a halide thereof with alkaline earthlmetal or with an alkali metal, it has been proposed to carry out the process in an atmosphere of argon. In operating on a substantial scale it will be obvious that the use of the necessarily large quantities .of a gas such as argon will be expensive and will materially add to the cost of the rare metals'which in themselves are expensive. Attempts to avoid the use of an expensive gas such as argon by carrying out the process in an atmosphere of a more readily available gas often leads to contamination of the product; e.g. the use of nitrogen often leads to the formation of nitrides. Again, while it is comparatively easy to reduce uranium compounds successfully in an atmosphere of hydrogen, it is found that if the melt of the metal is cooled in an atmosphere of hydrogen a comparatively large absorption of the hydrogen by the metal occurs during the process, leading to an impure product. The accompanying drawing diagrammatically illustrates an apparatus in which the present invention may be practised.

According to the present invention marked economies are achieved in the manufacture of metallic uranium by the reduction of a uranium compound with a more electropositive metal by carrying out the reduction step in a reducing atmosphere, and subsequently maintaining an atmosphere of argon above the resulting melt while the latter cools.

Suitably the reduction step is carried out in an atmosphere of hydrogen, though other reducing gases such as coal gas may be used.

The process may be applied, for example, to the manufacture of metallic uranium by reacting uranium tetrachloride, or the double salt of uranium tetrachloride and sodium chloride with an alkali metal such as sodium or an alkaline earth metal such'as calcium or magnesium, or with aluminium. Oxides of uranium may also be reduced with such metals, making use of this invention.

The process may also be applied, with advantage, to the method for the production of uranium described in copending application Ser. No. 505,321, filed October 7, 1943. In this application we have described the production of uranium by reacting anhydrous uranium tetrafiuoride with an alkali metal or an alkaline earth metal, including magnesium or with a mixture or an alloy of two or more of such metals. Preferably the reducing metal mixture or alloy has a boiling point above 1000 C. By. using the tetrafluoride as the source of uranium the reduction could be carried out without the use of closed pressure vessels, and, in general, the metal is obtained as a homogeneous mass beneath-an upper layer of slag.

The reaction could be carried out by heating a charge consisting of a mixture of the powdered or comminuted reactants containing excess of the reducing metal in a crucible until reaction is initiated. Alternatively, a small proportion of the charge .could be caused to react in the bottom of a suitably insulated hot reaction vessel, giving a fused mass, and the remainder of the reaction mixture could be added in small portions to thefused mass. It is thus possible to maintain the whole mass fused for a sufiicient time to allow the uranium to separate from the slag and thus form a regulus. The reduction process leading to the production of metallic uranium is carried out under an atmosphere of hydrogen which is suitably led into the top of the reaction vessel in which the reaction is carried out by an inlet tube through the lid. In adopting the method according to the present invention the inlet tube is fitted with two connections, one of which is to a source of hydrogen and the other to a source of argon. Normally it will not be necessary to provide for an exit tube as the cover will usually be loose enough .to allow for the escape of gas. During the reduction hydrogen is introduced through the, one connection, and when the reduction step is complete the supply of hydrogen is cut off and a small steady flow of argon started. The flow of argon will gradually replace the'hydrogen atmosphere and should, of course, be suflicient to prevent the leakage back of air into the crucible. The supply'of argon is normally maintained until there is an appreciable crust on the surface of the crucible contents.

An alternative method which we find preferable when operating on a small scale is to react a small portion of the reaction mixture in the bottom of a suitably insulated hot reaction vessel and to bring this to reaction giving a small fused mass. The remainder of the reaction mixture is then added in small portions at a time, each portion containing an excess of the reducing metal. Operating in this manner it is possible to maintain the whole mass fused for a sufiicient time to allow the uranium to separate from the slag, and thus for aregulus to be recovered.

An apparatus in which this may be efiected is illustrated in the accompanying drawing. In this drawing 1 is the crucible seated in a block of refractory material 2. The crucible has a lid 3 which is raised slightly at one side to admit the introduction of a chute 4 through which mixed reactants may be introduced. The lid 3 has a central opening through which projects into the crucible a pipe 5 for admitting hydrogen or argon. Pipe 5 is joined through a T piece to pipe 6 having a valve 8 through which hydrogen can be admitted, and to pipe 7 controlled by valve 9 through which argon can be admitted. Chute 4 and pipe 5 are supported in position by means not shown.

In using this apparatus pipe 5 and lid 3 are first raised to admit a blowpipe which heats up the crucible 1 and that part of refractory 2 immediately adjacent to it to a bright red heat. The blowpipe is then quickly removed, lid 3 and pipe 5 are put in position and a small charge of mixed reactants-is simultaneously introduced through chute 4 and hydrogen is introduced through pipe 5 by opening valve 8, valve 9 being closed. As the charge falls on the red hot crucible reaction occurs and the charge is fused. While it is still in a fused condition a further quantity of the charge is introduced which in turn reacts, and so on until all the charge has been added, which is suitably enough to fill the crucible to near the level of the chute 4. As the last charge is added, the valve 8 may be gradually turned off and valve 9 gradually turned on so that by the time the last charge has reacted an atmosphere of argon persists over the mass in the crucible. The flow of argon is continued until the mass Similar methods may also be employed in preparing uranium from other reactants such as the reaction of one of the oxides of uranium with calcium.

Working in this manner We have found it possible to tain yields of metallic uranium at least as high as those obtained hitherto and at the same time to effect a marked economy.

We claim:

1. In a process for the production of uranium by re ducing a uranium compound selected from the group con sisting of the oxides and the halogen compounds of uranium with a more electropositive metal, the steps of maintaining a reducing atmosphere above the mixture during the reaction, and when reaction is substantially complete displacing the said reducingatmosphere by an atmosphere of argon.

2, A process according to claim 1 in which the reducing atmosphere is a hydrogen atmosphere.

3. In a processrfor the production of uranium which comprises reacting a uranium'halogen compound with a substance selected from the group consisting of thealkali metals, the alkaline earth metals, (including magnesium) and mixtures and alloys composed of at least two of such metals, the steps of raising the temperature of a mixture of the uranium-halogen compound and the said substance until reaction is initiated while maintaining a reducing atmosphere abovethe said mixture, and when reaction is substantially complete but the reaction mixture is still molten, displacing the said. reducing atmosphere by an atmosphere of argon and allowing the reaction mixture to cool.

4. In a process for the production of uranium which comprises reacting a uranium-halogen compound with a substance selected from the group consisting of the alkali metals, the alkaline earth metals (including magnesium) and mixtures and alloys composed of at least two of such metals, the steps of raising the temperature of a mixture of the uranium-halogen compound and the said substance until reaction is initiated while maintaining a hydrogen atmosphere above the said mixture, and when reaction is substantially complete but the reaction mixture is still molten displacing the said hydrogen by an atmosphere of argon and allowing the reaction mixture to cool.

5. In a process for the production of uranium which comprises reacting uranium tetrafiuoride with a substance selected from the group consisting of the alkali metals, the alkaline earth metals (including magnesium) and mixtures and alloys composed of at least two of such metals, the steps ofraising the temperature of a mixture of the uranium tetrafiuoride and the said substance until reaction is initiated while maintaining a reducing atmosphere above the said mixture, and when reaction is substantially complete but the reaction mixture is still molten, displacing the said reducing atmosphere by an atmosphere of argon and allowing the reaction mixture to cool.

6. In a process for the production of uranium by reacting a uranium-halogen compound with a substance selected from the group consisting of the alkali metals, the alkaline earth metals (including magnesium) and mixtures and alloys composedtof at least two of such metals, the steps of raising the temperature of a mixture of, the uranium-halogen compound and the said substance until reaction is initiated while maintaining a reducing atmosphere above the said mixture, whereby a fused 'reaction mass is formed, adding further quantities of such a mixture so as to maintain the said reaction mass fused, while still maintaining the said reducing atmosphere above the reaction mass, and when the addition of such further quantities of reaction mixture is complete, displacing the Said reducing atmosphere by an atmosphere of argon, and allowing the said reaction mixture to cool;

7. In a process for the production of uranium by reacting a uranium-halogen compound with a substanceselected from the group consisting of the alkali metals,

the alkaline earth metals (including magnesium) and mixtures and alloys composed of at least two of such metals, the steps of raising the temperature of a mixture of the uranium-halogen compound and the said substance until reaction is initiated while maintaining a hydrogen atmosphere above the said mixture, whereby a fused reaction mass is formed, adding thereto, while still fused further quantities of such a mixture so as to maintain the said reaction mass fused, while still maintaining the said hydrogen atmosphere above the reaction mass, and when the addition of such further quantities of reaction mixture is complete, displacing the said hydrogen atmosphere by an atmosphere of argon, and allowing the said reaction mixture to cool.

8. In a process for the production of uranium by reacting uranium tetrafiuoride with a substance selected from the group consisting" of the alkali metals, the alkaline earth metals (including magnesium) and mixtures and alloys composed of at least two of such metals, the steps of raising, the temperature of a mixture of the uranium tetrafiuoride and the said substance until reaction is initiated while maintaining a reducing atmosphere above the said mixture, whereby a fused reaction mass is formed, adding thereto, while still fused further quantities of such a mixture so as to maintain the said reaction mass fused while still maintaining the said reducing atmosphere above the reaction mass, and when the addition of such further quantities of reaction mixture is complete, displacing the said reducing atmosphere by an atmosphere of argon, and allowing the said reaction mixture to cool.

9. In a process for the production of uranium by reacting uranium tetrafiuoride with a substance selected from the group consisting of alkali metals, the alkaline earth metals (including magnesium) and mixtures and alloys composed of at least two such metals, the step of raising the temperature of a mixture of the uranium tetrafiuoride and the said substance until reaction is initiated while maintaining a hydrogen atmosphere above the said mixture, whereby a fused reaction mass is formed, adding thereto, while still fused further quantities of such a mixture so as to maintain the said reaction mass fused while still maintaining the said hydrogen atmosphere above the reaction mass, and when the addition of such further quantities of reaction mixture is complete, displacing the said hydrogen atmosphere by an atmosphere of argon, and allowing the said reaction mixture to cool.

10. In a process for the production of uranium by reacting uranium tetrafiuoride with calcium, the steps of raising the temperature of a mixture of the uranium tetrafiuoride and calcium until reaction is initiated while maintaining a reducing atmosphere above the said mixture and when reaction is substantially complete but the reaction mixture is still molten displacing the said reducing atmosphere by an atmosphere of argon and allowing the reaction mixture to cool.

11. A process according to claim 10 in which the reducing atmosphere is a hydrogen atmosphere.

12. In a process for the production of uranium by reacting uranium tetrafiuoride with calcium, the steps of raising the temperature of a mixture of the, uranium tetrafiuoride and calcium until reaction is initiated while maintaining a reducing atmosphere above the said mixture, whereby a fused reaction mass is formed, adding thereto, while still fused further quantities of such a mix ture so as to maintain the reaction mass fused while still maintaining the said reducing atmosphere above the reaction mass, and when the addition of such further quantities of reaction mixture is complete displacing the said reducing atmosphere by an atmosphere of argon, and allowing the said reaction mass to cool.

13. A process according to claim 12, in which the reducing atmosphere is a hydrogen atmosphere.

(References on following page)- References Cited in the file of this patent UNITED STATES PATENTS 6 Kroll .Tune 25, 1940 Kjellgren Aug. 7, 1945 FOREIGN PATENTS Great Britain Dec. 10, 1925 OTHER REFERENCES Goggin: Cronin, Fogg and James, Industrial and Engineering Chemistry, vol. 18 (February 1926), pp. 

1. IN A PROCESS FOR THE PRODUCTION OF URANIUM BY REDUCTING A UNRANIUM COMPOUND SELECTED FROM THE GROUP CONSISTING OF THE OXIDES AND THE HALOGEN COMPOUNDS OF URANIUM WITH A MORE ELECTROPOSITIVE METAL, THE STEPS OF MAINTAINING A REDUCTION ATMOSPHERE ABOVE THE MIXTURE DURING THE REACTION, AND WHEN REACTION IS SUBSTANTIALLY COMPLETE DISPLACING THE SAID REDUCING ATMOSPHERE BY AN ATMOSPHERE OF ARGON.
 2. A PROCESS ACCORDING TO CLAIM 1 IN WHICH THE REDUCING ATMOSPHERE IS A HYDROGEN ATMOSPHERE. 